1. Field of the Invention
The present invention relates generally to enclosures for handling hazardous materials and, more particularly, to a controlled atmosphere work enclosure adapted to be used in dental operatories for mixing, mulling, cutting and storing amalgam.
2. Discussion of the Prior Art
Of major national concern are health hazards resulting from environmental pollution. Among the more deadly sources of pollution are the heavy metals, and of these mercury is one of the most hazardous and difficult to control.
Of particular concern are the hazards presented through careless handling of mercury in the dental office and dental laboratory. In fact, the abnormally high rate of suicide among dentists is believed by many experts to be directly linked to Mercury poisoning. Since the dental profession in the United States uses in excess of 200,000 pounds of mercury per year, or about four percent of the total amount used in the United States, a significant threat is presented, not only to the health of the dentist, but to his auxiliary personnel as well.
Environmental contamination through the use of mercury in dental operatories originates primarily from mercury spills and leakage or failure of mercury-containing capsules used in the trituration process. Also contributing to the inordinately high level of mercury contamination found in dental offices and laboratories is carelessness by the dentist and his assistants in mulling, amalgam cutting, and mercury storage. A recent study conducted at the University of Tennessee entitled "Mercury Vapor Experience in a Dental School Environment", JADA 88:785, April 1974, disclosed that seven out of ten dental operatories tested showed mercury vapor levels significantly above the threshold limit of 50 micrograms per cubic meter. This study further revealed that urinary mercury levels tended to parallel vapor exposure and that the urinary level of the average dentist was twice that of the accepted normal level (20.40 micrograms Hg/24 hrs. vs. 9.95 micrograms Hg/24 hrs).
One of the detrimental effects of excessive mercury exposure is acute anxiety. This factor is believed linked with metal illness and it has recently been established through statistical studies that dentists take their own lives twice as often as the general population.
Although mercury contamination poses a particular threat in dental offices and laboratories, the problem is by no means limited to such operatories. Wherever mercury is handled, be it in hospitals, scientific laboratories, or industrial plants, mercury contamination presents a significant health hazard. In hospitals and scientific laboratories, the mercury hazard arises from many sources, including the use of several pieces of apparatus such as the Coulter counter, the Van Slyke apparatus, Miller-Abbot and Cantor tubes.
In recent years, various approaches have been suggested to control mercury contamination in dental operatories, hospitals and laboratories. For example, several types of mercury vapor sensing devices have been developed to monitor mercury vapor levels. Similarly, a wide variety of filtered room exhaust units have been proposed to control atmospheric contamination. Little has been done, however, to prevent the contamination from occurring in the first place. Although expedients such as prepackaged amalgam capsule systems, wherein the mercury and alloy are stored and mixed in cartridges, have come into relatively wide use, such systems have exhibited several disadvantages. In addition to the propensity of the cartridges to leak during storage and to break during mixing operations, their handling and disposal after the amalgam is mixed contributes to environmental contamination.
The principal thrust of the present invention is to attack the mercury contamination problem at its source by providing a safe, compact, reliable, and easy to use controlled environment work station or enclosure wherein all routine mercury handling operations can be accomplished. As will be better understood from the discussion which follows, the work station of the present invention provides a totally enclosed, controlled environment workspace wherein various mercury handling operations such as mixing, mulling, and amalgam cutting, can be accomplished in absolute safety with no fear of personnel or atmospheric contamination. Mercury spills are completely contained within the unit and a novel air lock access arrangement is provided to enable the spilled mercury to be cleaned up without opening the unit to room atmosphere, thereby precluding any possible spread of contamination. All mercury handling operations are conducted through rubber gloves which are sealably connected to the unit so as to prevent personnel contamination through direct handling of the mercury. A unique air circulation system for controlling vaporous and particulate mercury within the system is provided so that a current of air continuously moves downwardly through and around the work platform toward a highly efficient mercury filtering medium. Specially designed filters are also provided at each air inlet port to prevent escape of mercury therethrough in particulate or vapor form.
The work enclosure of the present invention, when used in the dental operatory, is large enough to provide ample space to proportion, load, mix, cut, and store mercury and mercury alloys. Additionally, the work enclosure is designed to accommodate amalgamators of the latest design by providing a specially constructed platform upon which the amalgamator can conveniently be mounted.
Regular use of the work enclosure of the invention by the dentist and his assistants for all amalgam work virtually eliminates the threat of environmental contamination of the operatory with mercury.
When it is desired to use the work station of the invention in hospitals or scientific laboratories, it is to be appreciated that appropriate internal modifications can readily be made to accommodate numerous types of tools and instruments. Additionally, by use of special filters, the enclosure can readily be adapted to safely handle hazardous materials other than mercury such as toxic chemicals, radioactive materials, and the like.